Multiple signaling system



Feb. 16, 1937. F. R. BRIDGES MULTIPLE SIGNALING SYSTEM Filed oct. s1, 1932 Patented Feb. 1.6, 1937 2,071,060 MULTIPLE SIGNALING SYSTEM Frank R. Bridges, Needham, Mass., assigner to The Gamewell Company, Newton Upper Falls, Mass., a corporation of Massachusetts Application October 31, 1932, Serial No.,640,429

2 Claims.

The present invention relates to electric signaling systems for the purpose of communicating with persons expected to be present in the vicinity of an outer circuit or line of the system, whereby it may be possible to reach such persons with call signal devices placed at various points of the line, and whereby these persons may also be enabled to call, and to communicate with, a central station from the outer circuit. Wellknown installations of this type are the so-called police signaling systems which enable an ofiicer on duty to 'transmit from a patrol box code signals, so called report calls, to headquarters, for example at certain time intervals, so that his superiors may keep track of his movements and which in certain cases also permit the oiicer to reach headquarters with telephone calls. Headquarters must be able to reach an oiilcer with acoustic and/or optical so-called recall signals in order to call him to a patrol box from where a telephonie conversation may be conducted between the oillcer and headquarters, whereby the recall signal may or may not be at the same point as the patrol box.

Heretofore, arrangements of this type consisted oi two separate direct current systems, one the so-called patrol line, for making report calls to headquarters from points alongthe line and for telephone communication, whereas another direct current system, often referred to as recall circuit, permits headquarters to actuate recall signal devices distributed along this second circuit. Since these installations necessarily involve widespread networks and require constant readiness for emergency purposes, their erection and maintenance is rendered considerably more expensive by the duplication of line conductors constituting two separate coextensive systems for very closely related purposes. It is the main object of the present invention to provide a signaling system of the type described, which permits simultaneous operation of a patrol line circuit and a recall circuit with a minimum number of conductors for both circuits. A further object is the selective operation of recall signal devices of different character by using the same line which is employed for the patrol circuit. Still another object is the selective operation of different types of call signal devices with alternating current;

According to one aspect of the invention, the signal circuit is normally energized with direct current, and report calls, as well as telephone calls from the patrol boxes to headquarters, are transmitted by means of this direct current. The

same line also carries alternating current which is employed for actuating the recall signal de' vices from headquarters, whereby, according to one embodiment, currents of diierent characteristics may be used for selectively operating signal devices of diilercnt types as, for example, acoustic and optic signals.

In another aspect, the invention contemplates the operation of the recall signaling devices with alternating current instead of direct current, which is preferable to the operation with direct current, because the comparatively large number of signal devices which are to be Simultaneously operated necessitates in many cases` comparatively high energies which can be much more easily and economically supplied from alternating current sources instead of storage batteries, concerning initial cost as -well as maintenance. These and other objects and aspects of the invention will be better understood from the following detailed explanationk illustrating the genus of the invention by describing several concrete embodiments thereof The description refers to a drawing in which:

Fig. l is a simplied connection diagram of a complete signaling circuit according to the present invention;

Fig. 2 is a similar connection diagram of a modified recall signal circuit; and

Fig. 3 is a similar connection diagram of a 3 modified report and telephone call circuit.

In Fig. 1, S denotes a central station, for example located at police headquarters, with station terminals I and 2, from which an outer signaling circuit L with conductors 3 and 4 leads 35 to the district which is served by the circuit in question.

At the central station, a suitable source of direct current as, for example, a battery B supplies station busses 5 and 6, connected to terminals I and 2 respectively, and therefore the whole circuit, with direct current of suitable voltage which will depend upon the extension of the circuit, and other local characteristics/of the system. The central station further has a report call receiver D selectively actuating a recorder circuit R and/or a signal circuit L. This report call receiver will be described in detail hereinafter. An electric filter F of conventional design, which may consist of two inductances 2i, 22 and two capacitances 23 and 24 of suitable dimensions, substantially prevents alternating current from reaching the report call receiver and the battery. It is understood that any arrangement suitable for this purpose may be used instead of the con- 55 ventional filter shown, and that, for example, a rectifier arrangement or choke coils without con'- densers may be used for this purpose, according I to the more or less exacting requirements of the particular installation.

'I'he central station further comprises telephone connections T which comprise two condensers II and I2 respectively, a telephone plug or key switch I5 and leads I1, I8 to a conventional telephone switchboard.

The central station further comprises a recall sender A which consists in the embodiment shown in Fig. 1 of a signaling switch 3|, actuated by a code wheel 32, and in series with a condenser 33 and the secondary 34 of a transformer having two primaries 35 and 36. 'I'he transformer primaries are connected to terminals 4|, 42, 43, 44 respectively, through switches I0 and 20. Terminals 4I, 42, and 43, 44 respectively are connected to alternating current circuits supplying distinct frequencies as for example, cycles per second across terminals 4I, 42 and cycles per second across terminals 43, 44. It is understood that any suitable instrumentalities maybe used for supplying these alternating currents to the recall sender as, for example, two distinct alternating current generators, or duplex machines, or oscillator circuits employing electronic devices.

Along the line or outer circuit are distributed patrol box stations or report call transmitters C, which comprise signaling switches 5I operated by code wheels 52 across the two line conductors 3 and 4, and report call telephones which are herein schematically indicated by a microphone M, a receiver N, a transformer 54, a condenser 55, and a hook switch 56, which devices afford a so-called Western telephone circuit which, however, may be replaced by any telephone arrangement suitable for the present purpose.

'Ihe outer circuit is further connected to recall relays P. In the present embodiment, these relays consist of two magnets 6I and 62 connected across the two conductors in series with condensers 63, 64 and inductances 65, 66 respectively, the magnet windings, the inductances and capacitances forming selective circuits, each circuit being resonant to a respective predetermined frequency. Due to this arrangement, which may be replaced by any other circuit suitable for this purpose, the magnets 6| and 62, respectively, respond only to alternating currents of the respective frequencies of the recall sender A, so that for example in the present instance magnet 6I responds substantially only to alternating current of 80 cycles per second and magnet 62 only to alternating current of 110 cycles per second. 'I'he armatures of magnets 6I and 62 are adapted to actuate normally open switches 68 and 69, respectively. Switch 68 controls a local signaling circuit comprising power supply busses 1I and 12 and a signal lamp 13. Switch 69 is similarly part of a local signal circuit containing a sound generator herein indicated as a bell 15.

The report call receiver D of the central station comprises magnets 8l and 82, each of which consists of two winding portions serially connected in the station busses, as shown in Fig. 1. These magnets are adapted to actuate normally open switches 83 and 84 in the following manner. The windings of the two magnets have different reslstances; for example, the windings of magnet 8l may have a resistance of 14 ohms and the windings of magnet 82 a resistance of 194 ohms, so that only relay 8|V is sufiiciently energized by a comparatively weak current for closing switch 84, whereas both magnets 8i and 82v are sufilciently energized by a comparatively strong current to close both switches 63 and 84. Switch 83 is part of the local recorder circuit R which comprises local power supply busses 9i and 82, and a recorder magnet 93 which may directly actuate a means for graphically recording incoming code signals, or indirectly control a separate conventional recorder` circuit. The switch 84 is part of a local lamp circuit L comprising the local current supply and a signal lamp 86 which indicates energization of relay magnet 8|.

It is understood that any desired number of patrol boxes C and recall relays P with their signaling devices may be distributed along the outer circuit, whereby the devices P and C may be at different points of the line. or at the same points, as indicated at P', C and PC ot Fig. l.

This embodiment of my invention operates in the following manner. If an ofiicer during his round of duty wants to despatch the periodical report call signifying that he has been at a certain point at a certain time, he opens the respective signal box C and causes the code wheel 52 to turn so that switch 5I establishes connections between conductors 3 and 4 in correspondence with the report call signal which is allotted to that particular box. 'I'he direct current impulses corresponding to this signal pass filter F of the central station and cause both magnets 8l and 82 to attract their respective armatures and close switches 83 and 84. In the outer circuit, this current has only to overcome the line resistance and is therefore strong enough sufciently to energize the coils of magnet 82 as well as the coils of 8|. Switch 83 closes and opens local circuit R in accordance with the code impulses, which insuitable conventional manner causes the recording of the incoming signals, for example on a tape. Iamp 96 flashes in accordance with the code signal, thereby indicating that the officer on the beat gives his periodical report call but does not desire to carry on a conversation with headquarters.

If the omcer desires to talk with headquarters he takes oi hearer N, thereby connecting conductors 3 and 4 through hook contact 56. The direct current circuit closed thereby includes the high resistance of the telephone circuit and is therefore only strong enough to energize magnet 8l for closing switch 84 but it is not sufliciently strong to energize magnet 82, so that switch 83 remains open. Lamp 96 begins to light continuously, indicating that a conversation is desired, whereupon the operator at the supervisors desk at headquarters closes, by conventional means, telephone switch I5 of telephone branch T, thereby connecting the oilicer to a suitable telephone switchboard through conductors I1 and I8.

If headquarters desire to call an oilicer to one of the points of the line which are provided with recall apparatus, one or both switches III and 2D are closed and subsequently thereto code wheel 32 is actuated. Switch 3| thereupon despatches alternating current code signals to outer circuit L, which are received at relays P. Assuming, for example, that only switch I Il has been closed, the alternating current code impulses of a frequency of 80 cycles energize only magnet 6I, which is part of the circuit resonant to that frequency. Magnet 6I closes switch 68, thereby causing signal lamp 13 to ash in accordance with the code signal despatched by means of acumen code wheel 32. If only switch 20 has been closed, the acoustic signal 15 operates in a similar manner with alternating current of 110 cycles. If both switches and 20 are closed, optic and acoustic signal devices can be actuated simultaneously.

It will be observed that the direct current which establishes connection between C and D is not able to inuence the alternating current signaling means A .and P because these are blocked against direct current by condensers 33, 63, and 64. On the other hand, alternating current can not reach the receiver D because of the filter F. `It is therefore apparent that signal transmission with both alternating and direct currents can be carried on independently and simultaneously, whereby it is understood that only one, or more than two alternating current frequencies may be utilized.

Figure 2 shows another possibility for operating at will one or two, or both, kinds of recall signals. In this ligure 3 and 4 are again the conductors of the outer circuit which are connected to the busses 5 and 6 of the central station through station terminals and 2. Report call receiver and report call transmitters are arranged similarly as shown in Fig. 1 and therefore only indicated in Fig. 2. Instead of utilizing alternating current of two frequencies and frequency selective devices at the recall relays, the following arrangement is provided. A transformer secondary |34 supplied with energy from primary |35, which is connected to a suitable source of alternating current, is on the one side grounded through a condenser |33 and signaling switch |3| with code wheel |32, and on the other side connected to a conductor |04 in termediate two switches ||0 and |20 serially connected by conductor |04 across busses 5 and 6. The receiving station P comprises flash signal relays |6| and |62 which are on the one side connected to ground, and on the other side to conductors 3 and 4 respectively, through condensers |63 and |64, respectively. It will now be apparent that by closing switch ||0 and/0r switch |20, optic and/ or acoustic signals can be despatched at will. This arrangement is somewhat simpler than that shown in Fig. 1, but it employs the ground as a conductor, which may be undesirable in certain cases for reasons Well known in the art.

Sometimes it is advantageous not to use marginal relays, as shown at 8| and 82 of Fig. 1, which, under certain circumstances, are not as reliable as might be desired. In such cases a modified arrangement, as shown in Fig. 3, may be employed. In this instance the battery B is connected between ground and a conductor bridging busses 205 and 206 which are again connected to line conductors 203 and 204 through station terminals and 202. Patrol box stations C comprise, similar to the embodiment shown in Fig. 1, coding devices with code wheels 232 and switches 23|, and telephones with receivers N, microphones M, hook switches 256, transformers 254 and condensers 255. The coding' devices are connected between conductor 203 and ground, and the telephones between conductor 204 and ground. It will be apparent that a third conductor may be employed instead of the ground, especially for improving the quality of telephonie communications between box stations and headquarters. The report call receiver D, as shown in Fig. 3, comprises a conventional relay 282 connected in bus 206, a similar relay 28| in bus 206, and corresponding switches 263 and 284 controlling local circuits R and L, respectively. 'I'he remaining elements ofA the circuit, namely filter F, telephone connection T. recall sender A, and recall relays P are similar' to those shown in Figs. l or 2, and are therefore only schematically indicated in Fig. 3.

The operation of this modification is quite analogous to that of the previously explained modifications and can be understood without further explanation. It will be suilicient to point out that coding devices 23|-232 actuate a recorder in circuit R, and that telephone calls are indicated by a. signal device in circuit L.

It will be apparent to anyone familiar with this art that the modication shown in Fig. 3 may be combined'with the alternating current circuits of either Fig. 1 or Fig. 2, and that several other variations are feasible as, for example, a comof Figs. l and 2.

It should be understood that the presentdis closure ls for the purpose of illustration only and that this invention includes all modiiications and equivalents which fall within the scope oi the appended claims.

Iclaim:

l. A signaling system comprising an outer circuit of two metallic lines, a central station with a direct current source normally connected to said outer circuit and a single direct current code signal receiver in series with said source, a. plurality of code wheel signal senders connected at different outer stations in parallel to said outer circuit for despatching different signais to said central station by opening and closing said circuit for said source and said receiver, means in said central station for substantially shielding said direct current source and said direct current receiver against alternating currents, a code wheel operated signal transmitter likewise in said central station permanently connected for despatching different alternating current code signal impulses into said outer circuit for calling said outer stations, means substantially excluding direct current at said station intermediate said transmitter and said outer circuit, an alternating current code signal receiver in each outer station in parallelwith each code signal sender, and direct current excluding means intermediate said outer circuit and said alternating current receivers, whereby predetermined code signals can be despatched from various points of said outer circuit to said station, and simultaneously from said station to said points of the outer circuit.

2. A signaling system comprising an outer circuit of two metallic lines, a central station with a direct currentsource normally connected to said outer circuit and a single direct current code signal receiver in series with said source, said receiver being selectively responsive to direct currents of different strength, a vplurality of code wheel signal senders connected at different outer stations in parallel to said outer circuit for despatching different signals to said central station by opening and closing said circuit for said source and said receiver, telephones grouped with said senders and in calling position closing said circuit through a highresistance for actuating said receiver with current of lower strength, means in said central station for substantially shielding said direct current source and saiddirect current receiver against alternating currents, a telephone in said central station directly on said outer circuit, a code wheel operated signaltransmitter likewise in said central station permanently connected for despatching different a1- ternating current code signal impulses into said outer circuit for calling said outer stations, means substantially excluding directcurrent at said station intermediate said transmitter and said outer circuit, an alternating current code signal receiver in each outer station in parallel with each code signal sender, and direct current'excluding means intermediate saidA outer circuit and said alternating current receivers, wherebyl predetermined code signals and telephonie messages can be despatched from various points of said outer circuit to said station, and from said station to said points of the outer circuit.

, FRANK R. BRIDGES. 

